The present invention relates to a system for connecting valve units for gas water-heaters to tanks belonging to the water-heaters.
In the specific technical field of the present invention, there is a need to connect gas-valve units to tanks of the type generally used in water-heaters for domestic heating. Typically, in these applications, the tank has a hole into which a tubular body is screwed in a leaktight manner; a regulation probe, for example, a thermostatic bulb, extends through the tubular body and is supported thereby and housed inside the tank. Means are provided on the tubular body and on the valve unit for clamping the valve unit and the tank to one another axially.
A connection system of the type indicated is known from U.S. Pat. No. 5,261,438. The system described therein provides for the valve unit to be clamped axially by means of a spring ring which is mounted externally on a shank projecting from the valve unit and which can engage an annular groove formed inside the tubular body screwed into the tank. The insertion of the shank into the tubular body from the front causes the resilient ring to be engaged in the groove, connecting the valve unit axially to the tank.
One of the problems encountered in this system is that the coupling between the valve unit and the tubular body is irreversible and, once the valve unit is connected to the tank, it can be disconnected only by completely unscrewing the tubular body. This operation therefore renders maintenance operations on the apparatus with which the valve unit is associated rather complex.
This system also involves a fairly complex structure as well as a valve unit which is fairly bulky axially, mainly because of the projecting shank provided for the mounting of the clamping spring ring.